CatSpin:
First of all congratulations on your "comeback." Finding joy in your riding is what riding is truly about, regardless of whether you race or just ride for fun.
Think of how much power is lost every time your rear wheel comes off the ground. You need to correct this.
To correct the problem, practice your uphill sprints at a very low speed in a very low gear like a 39x25 or 39x27. Don't focus on speed at all. The goal is to practice the mechanics/technique of your uphill sprint.
Your technique is very important, and really can't be practiced at high power output. In slow-to-medium motion, do your sprints.
Even though you are doing them slowly, you will probably feel where in your stroke you are lifting the wheel off the ground. Because your power output will be much lower, you probably won't raise the wheel off the ground, but it might feel like it is starting to.
Most importantly, you should also move back more towards the tip of your saddle. Lots of riders sprint standing straight up, close to the stem and bars. This is bad form. You will get more power transfer from your hips and glutes if you sprint with your back flat and butt closer to the tip of your saddle.
When climbing out of the saddle, you should occasionally brush the tip with your butt to make sure your are back far enough. Climbing or sprinting too close to the bar/stem will tire your legs prematurely and not maximize power output, since you are not fully recruiting the hips and glutes.
It also takes strong abs to support the body with your back parallel to the ground compared to standing straight up, and that is the "path of least resistance" many riders take. They don't like to feel the extra pressure in their abs. Don't take the easy way out. Take the path of the "harder right" versus the "easier wrong." Correct technique will maximize power output.
The best athletes in the world, regardless of sport, practice the mechanics of their sport at very low speeds to ensure correct form. It could be kicking a soccer ball, swinging a baseball bat, or pedalling a bicycle.
If your technique is bad, all you will do at high speed/power output is amplify your mistakes. You can only practice the correct technique at slow speeds/slow motion. This is yet another reason why isolated leg training (ILT) improves your stroke and power output. If you have ever ridden behind a rider who does ILT, you might mistake them for a professional, because their spin is so smooth and beautiful.
Do several low-speed "technique" drills to correct your form, recover for a few minutes, then apply what you have learned in full-power sprints.
Since you are a spinning instructor, make sure your spinning bike is set up identical to your road bike, with the same saddle height and saddle setback, and bar/stem height distance. Ideally, you would have the same pedal system and cranklength as well. When you are sprinting in class, be sure to apply the correct technique as well.
The body does what it is trained to do. If you practice incorrectly, you will race incorrectly. Technique is critically important. Neglecting it will prevent you from reaching your full potential as a rider.
Good luck!!!
